The present invention relates to the development and use of a solid gas generating composition which, unlike the sodium azide based gas generating compositions which are currently widely use to inflate airbags in motor vehicles, uses a non-azide chemical compound as the fuel. The non-azide chemical compound reacts with a multi-oxidizer system to generate nonhazardous gases, primarily containing nitrogen. The gases so liberated have been primarily designed to fill airbags used in the automobile industry, but other uses can also be visualized for such gas generating compositions.
The present invention is primarily directed towards the automotive airbag industry, which has historically had to deal with toxicity issues. The airbag systems currently produced most often use gas generating compositions based on sodium azide as a fuel in combination with metallic oxidizers. The use of sodium azide has a number of advantages. It is a solid, easily produced in a high degree of purity, and can be used to prepare gas generating compositions in combination with one or more metallic oxidizers, to yield solid gas generating compositions at very reasonable costs. However the greatest disadvantage of sodium azide is its high toxicity. The ingestion of even small amounts of sodium azide in a human could cause a rapid decrease in blood pressure and even death. This toxicity problem is potentially accentuated as the cars with sodium azide in the airbag system get scrapped. If the gas generating devices of airbag systems containing sodium azide are not removed from vehicles before scrapping, they could cause an environmental hazard.
To overcome this problem, various approaches have been taken by the airbag industry, one such approach being the use of stored gases to fill the airbags. The gases are stored at high pressure in a cylinder with a rupture disc. The rupture of these discs is triggered by a crash pulse, picked up by an electro-mechanical or electronic sensor. The gases used are inert gases like helium and argon. A variation of the same employs a pyrotechnic gas generating composition, the heat of which is used to raise the temperature of the gas in a stored gas system and is commonly referred to as a hybrid system. There are number of patents covering stored gas and hybrid systems. Examples of these types of systems are taught for example in U.S. Pat. No. 5,344,186 and U.S. Pat. No. 5,345,876. While the stored gas and hybrid systems give a clean inflation gas, with very little or no particulate, they are cumbersome and difficult to make function at the high and low temperature extremes required by the industry. Also the stored gases could leak during a long storage period.
The present invention overcomes most of these problems with a gas generating composition which is a solid, easily manufactured and has good storage properties. Furthermore, most of the equipment used in the manufacture of sodium azide based gas generating compositions can be used in the manufacturing of these non-azide generating compositions.